Effect of reduction of blood volume on plasma immunoreactive atrial natriuretic factor concentrations in normal man

Plasma immunoreactive atrial natriuretic factor (i-ANF) concentrations were measured in ten voluntary blood donors before and after acute blood loss induced after they had been supine for 20 min. Lying down caused i-ANF to increase significantly in all subjects. Bleeding (400 ml in 5 min) caused i-ANF to decrease to values significantly lower than either those observed before haemorrhage or those recorded in the upright position. These results provide evidence that in normal man acute changes in the intravascular volume, although limited within physiological limits, are able to induce opposite changes in i-ANF release.